SE/B06/011: 6 of one, half a dozen of the other!
Man on bed
Back to St Emlyn's Reception

1. Interpret the blood gases.
This is a very interesting set of gases. The patient has a normal blood pH, so no acidaemia or alkalemia. However, they have a high lactate, which you would expect to be associated with a metabolic acidosis. They also have a high base excess indicating a metabolic alkolisis. These two factors are balancing themselves out and this is one of those situations where it is so important to look at all of the findings on the blood gas.

But why the metabolic alkalosis in this patient? In fact it is due to a hypochloraemic state that exists probably as a result of the vomiting and the duiretics.

We are fortunate in having a blood gas machine in the resus room that gives this kind of information as soon as the patient has vascular access. Many of our trainees say that they cannot imagine rotating to another hospital without access to early lactates and biochemistry.

2. What do you think of venous blood gases?
We are great advocates of their use in the emergency department. There is almost as much information available on a VBG as on an ABG, and if you combine this with non-invasive puse oximetry for oxygen saturations you can rapidly get a global picture of how the patient is. We are certainly moving away from serial arterial sampling in patients with conditions like DKA etc.

Still in doubt????? Ask yourself whether you would let someone take a venous test from you as part of a trial??? You may well, but would you let them take an arterial? Most doctors wouldn't, and if it is not good enough for us, it should not be acceptable for patients either.